Neutron activation analysis of low level lithium in water samples

For determining low level lithium concentrations in water, a neutron activation method based on the measurement of tritium radioactivity produced by⁶Li(n,)³H reaction has been developed. This method is specific and free from interference by other chemical elements. Using a low background liquid scintillation counter for tritium measurement, the detection limit is approximately 0.3 ppm during irradiation at a thermal neutron flux density of 1.1·10⁷n·cm^–2·s^–1 for 6 hours by a small nuclear reactor and liquid scintillation counting for 2000 minutes     

Determination of lithium in graphite by neutron activation analysis

Trace impurities of lithium in graphite is one of the sources of tritium in high-temperature reactors. To determine contents of less then 1ng/g a procedure based on the (n,)-reaction of⁶Li was developed. The samples are irradiated in a reactor and then ignited in a Wickbold apparatus. Thereby the tritium produced by the (n,)-reaction is completely converted in HTO, which can be easily purified by distillation and, if necessary, by a scavenger precipitation step. Several types of graphite have been investigated and the lowest content measured was 0.2 ng/g.     

Determination of lithium isotopic composition by thermal ionization mass spectrometry in seawater

The isotopic composition of lithium in seawater has been determined by thermal ionization mass spectrometry (TIMS) based on the use of lithium hydroxide as the ion source. Isotopic measurements in a reference material supplied by IAEA (L-SVEC Li₂CO₃) were made to check the reproducibility of the method and ⁶Li indicates mobilization of light isotope of lithium form the sediment.     

Isotopic analysis of lithium by prompt alpha measurement during deuteron irradiation

Charged particle spectrometry was used to determine the isotopic concentration of lithium in lithium fluoride targets irradiated with a deuteron beam of 4.0 MeV. Alpha particles emitted by the⁶Li(d, α)⁴He and⁷Li(d, α)⁵He reactions were used as a measure of⁶Li and⁷Li, respectively. From the⁶Li/⁷Li α-count ratio the isotopic concentration of⁶Li was determined for isotopic concentrations over the range 7.42 (natural) to about 30 atom%⁶Li, with a relative standard deviation of±4.1%. Alpha particles from the¹⁹F(d, α)¹⁷O reaction could also be measured as an internal standard, extending the measurements from natural to 100 atom%⁶Li and giving a relative standard deviation of ±1.9%. The effect of target thickness on the accuracy of the determinations was investigated.     

Atomicm absorption spectrometric determination of the isotopic composition of lithium by an ultimate absorbance-ratio technique

The conventional absorbance-ratio technique for determining the isotopic composition of lithium by atomic absorption spectrometry is improved by the use of “ultimate absorbance ratios” of sample solutions. These ratios are obtained by extrapolating the linear portion of lithium content/absorbance-ratio plots to the intercept at 0 mol m^?3 lithium. These graphs are obtained measuring the absorbances of solutions of known ⁶Li abundance and of various lithium contents with natural and ⁶Li-enriched lithium hollow-cathode lamps. Linear calibration is attained over the range 0.0–99.3% ⁶Li, and the lithium isotopic abundance can be determined with an absolute error of ±0.7% ⁶Li for > 0.01 mol m^?3 lithium solutions. The method requires neither prior measurement of the total lithium content in sample solutions nor adjustment of the content to match that in the standard solutions.     

Studies in neutron depth profiling

This paper describes first the application of neutron depth profiling (NDP) for measuring the distribution of⁶Li in LiAlO₂ ceramics. Using a surface barrier detector for detecting³H produced in⁶Li(n, )³H,⁶Li was profiled to a depth of 14 m in the ceramics. Secondly, a new methodology is presented for NDP with enhanced capabilities based on measuring the energy of recoiling nuclei from (n, p) and (n, ) reactions by time-of-flight mass spectrometry. The scope of recoil nucleus time-of-flight mass spectrometry (RN-TOF-MS) includes profiling of¹⁰B,¹⁴N,¹⁷O,³³S,³⁵Cl,⁴⁰K. Probe depths may be of a few tens nanometers. RN-TOF-MS complements and refines NDP based on charged particle (p or ) spectrometry.     

Yields of fission products with masses A=131 to 135 for the fast neutron induced fission of U-238

Yields of eleven fission products with masses A=131 to 135 have been determined for the reactor neutron induced fission of²³⁸U by means of radiochemical separation combined with high-precision Ge(Li) -ray spectrometry. The charge distribution in the isobaric chains 131 to 134 and the isotopic distribution of₅₂Te have been studied.     

High‐precision determination of lithium and magnesium isotopes utilising single column separation and multi‐collector inductively coupled plasma mass spectrometry

Rationale

Li and Mg isotopes are increasingly used as a combined tool within the geosciences. However, established methods require separate sample purification protocols utilising several column separation procedures. This study presents a single‐step cation‐exchange method for quantitative separation of trace levels of Li and Mg from multiple sample matrices.

Methods

The column method utilises the macro‐porous AGMP‐50 resin and a high‐aspect ratio column, allowing quantitative separation of Li and Mg from natural waters, sediments, rocks and carbonate matrices following the same elution protocol. High‐precision isotope determination was conducted by multi‐collector inductively coupled plasma mass spectrometry (MC‐ICPMS) on the Thermo Scientific™ NEPTUNE Plus™ fitted with 10¹³ Ω amplifiers which allow accurate and precise measurements at ion beams ≤0.51 V.

Results

Sub‐nanogram Li samples (0.3–0.5 ng) were regularly separated (yielding Mg masses of 1–70 μg) using the presented column method. The total sample consumption during isotopic analysis is <0.5 ng Li and <115 ng Mg with long‐term external 2σ precisions of ±0.39‰ for δ⁷Li and ±0.07‰ for δ²⁶Mg. The results for geological reference standards and seawater analysed by our method are in excellent agreement with published values despite the order of magnitude lower sample consumption.

Conclusions

The possibility of eluting small sample masses and the low analytical sample consumption make this method ideal for samples of limited mass or low Li concentration, such as foraminifera, mineral separates or dilute river waters.

     

CBNM - determination of Li in BCR reference materials RM 303 and RM 304 lyophilized serum by isotope dilution mass spectrometry (IDMS)

Summary Lithium was determined in two BCR Candidate Reference Materials 303 and 304 by Isotope Dilution Mass Spectrometry using the state-of-the-art performance of isotope-specific methods gained during previous certifications of ⁶LiF reference targets used for the determination of the neutron lifetime [1]. After reconstitution of the serum, four aliquots of each of the two candidate materials from four different bottles were spiked with a previously characterized enriched ⁶Li spike [2] which is now available as CBNM IRM-615 and has a certified ⁶Li/⁷ Li ratio of 21.78±0.12 and a certified lithium concentration of 4.001±0.028 mol/g solution. The serum aliquots were digested in an HNO₃/H₂O₂ mixture and after evaporation of the acid, the lithium was separated on a cation exchange column, eluted with 0.3 mol/L HCl and used as LiCl for mass spectrometric measurement on an NBS type thermal ionization mass spectrometer. Similarly an unknown sample BCR X, provided by BCR to check the performance of the certifying laboratories, was analyzed. In addition the chemical preparation method was controlled by assaying NBS (NIST) SRM 909. The chemical blank was determined by IDMS using ⁶Li enriched CBNM IRM-615. The measurements were corrected for isotopic fractionation using the Isotopic Reference Material CBNM IRM-016 chemically prepared in the same way as the samples. The CRM samples as well as the BCR X sample and the NBS SRM 909 were also analyzed for isotopic composition to verify whether they had indeed natural isotopic composition. The final results have an overall uncertainty of 1.2 and 1.5%, respectively. This overall uncertainty (on a 2s basis or an estimate thereof) takes into account all uncertainty contributions of statistical as well as of systematic nature (uncertainties on used reference materials, density and blank determinations). The final results compare favorably with the values proposed by BCR for certification, but have a smaller (better) uncertainty: CRM 303: (0.517 4±0.005 7) mmol/L, CRM 304: (0.987±0.014) mmol/L     

Determination of tritium in Li–Pb alloy irradiated by thermal neutrons with quantitatively analyzing the byproduct 4He

The mass of the tritium produced in ⁶Li(n,α)T reaction was obtained by quantitatively analyzing the byproduct ⁴He with mass spectrometer. The self-expending seal method was employed to quantitatively prepare the Li–Pb alloy targets in room temperature. They were irradiated for 2 h in two rabbit irradiation channels in Xi’an pulsed reactor and measured after cooling 15 days. A sample purifying unit was set up to get rid of the hydrogen isotopes to remarkably reduce the interference to helium isotopes when measuring. And the sample disposal platform including purifying unit was testified with simulative gas and nature atmosphere. The targets were melted at 700 °C to release most of the ⁴He atoms which were measured by adding dilution gas ³He. And it was testified that ⁴He had released completely by repetitiously melting the targets. This approach had solved the problem that the tritium couldn’t be accurately determined by directly analyzing it because of non-complete releasing from lithium alloy.     

Transport Properties of Solid Electrolytes: Effect of the Isotope Composition of Lithium Charge Carriers

The isotope composition of lithium charge carriers is experimentally found to severely affect transport in solid electrolytes -Li₃BO₃, Li₃N, Li₃AlN₂, Li₅SiN₃, Li₆MoN₄, Li₆WN₄, and LiCl. The lithium cation conduction of these decreases with increasing content of ⁶Li or ⁷Li and reaches a minimum at [⁶Li] = [⁷Li]. The activation energy for conduction increases, reaches a maximum in the same compositions, and then diminishes. Rates of spin–lattice relaxation of ⁷Li nuclei in electrolytes are studied by an NMR method at 15–35 MHz. The calculated activation energy for short-range motion (to one interatom distance) of lithium charge carriers in crystal lattices of electrolytes is lower than that for ionic conduction by 2–3 times, which is attributed to two types of correlation (electrostatic, isotopic) of charge carriers.     

The neutron activation determination of lithium in the presence of alkali metals and magnesium

A neutron activation method for lithium in the presence of alkali metals or magnesium has been developed, utilizing the ⁶Li(n,α)³H and ¹⁶O(t,n)¹⁸F nuclear reactions. After a short thermal neutron irradiation with a. lithium standard, 112-min fluorine-18 is separated by a lead chlorofluoridc precipitation. The annihilation photons from the separated fluorine-18 are counted using 2 sodium iodide detectors, a fast-slow coincidence system and a multichannel analyzer. Precision in a synthetic l% lithium-in-sodium matrix was found to be ± 2.0% standard deviation, whereas the accuracy of the method is estimated to be ± 3% or better. The ultimate sensitivity in pure solution is estimated to be about 0.2 p.p.b. and in a sodium matrix about 0.5 p.p.m. The only interferences are several positron emitters, easily discriminated from by chemical separation, decay or by means of other nuclear parameters. Three hours are required for a duplicate determination, following initial sample preparation and dilution. To use the method, the lithium isotopic abundance must be known or determined by mass spectrometry because of the prevalence of depleted litliium in metal and salts.     

Determination of13C in breath sample by PIGE

This paper discusses a novel application of PIGE for the determination of¹³C in breath. Samples of human breath, urea, glucose, benzamide, barium carbonate were analyzed against cylinder CO₂ and graphite standard. An accuracy check of the¹³C determination (with reference to mass spectrometric True results) gave a relative error of only –0.4% for PIGE. The performance of different standards in this determination was assessed. Relative standard deviation for the determination of¹³C isotopic abundance in breath samples were <20%. Then, if a 25% change is conservatively assumed observable in¹³C abundance, an increase in¹³C percent isotopic abundance from the natural 1.11% (average) to only 1.39% may be detected.     

Heliuim-3 mass spectrometry for low-level tritium analysis of environmental samples

Helium-3 (³He) mass spectrometry for the analysis of low-level tritium (³H) concentrations (0.5 to 5 Bq·l^–1) in environmental sample matrices was compared with conventional low-level -decay counting methods. The mass-spectrometry method compared favorably, equalling or surpassing conventional decay-counting methods with respect to most criteria. Additional research and method refinements may make³He mass spectrometry the method of choice for routine, low-level to very-low-level (L<0.5 Bq·l^–1)³H measurements in a wide variety of environmental samples in the future.     

Accurate and precise lithium isotopic determinations of igneous rock samples using multi-collector inductively coupled plasma mass spectrometry

A second-generation multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) was applied to lithium isotopic measurements. The high sensitivity of the ICP-MS enabled high precision (±0.82‰, 2σ) analyses with small amount of Li (∼45 ng Li). A single-step column separation protocol was established with which rapid purification of lithium from rock solutions can be carried out with reduced blank (<10 pg). The influence of potential sources of error for acquisition of lithium isotopic data introduced during the separation, such as matrix effects and isotopic fractionation due to incomplete recovery, were examined with an artificially mixed solution of a composition similar to that of basalt, which was doped with Li isotopic standard reagent. The examinations demonstrated that our protocol suffered from negligible isotopic fractionation.The Li isotopic ratios obtained by our method for seawater and standard rocks (JA-1, JB-2, and JB-3) agree well with those of previously reported data by Moriguti and Nakamura [1] and [2], which were determined using a four-step column separation method and thermal ionisation mass spectrometry (TIMS). Our separation protocol combined with a sensitive MC-ICP-MS will enable Li isotopic analyses on silicate rock with low Li contents, such as meteorite and peridotites with increased sample throughput.     

Measurement of the radioactivity of238U,232Th,226Ra,137Cs and40K in soil using direct Ge(Li) γ-ray spectrometry

Radioactivity of the nuclides²³⁸U(²³⁵U),²³²Th,²²⁶Ra,¹³⁷Cs and⁴⁰K was measured in soil by direct -ray spectrometry using Ge(Li) detector. Relative laboratory method was used. Soil was dired, powdered, sieved and put into hemetically sealed container. CCRMP certified reference materials and compounds of the above nuclides mixed with fine quartz sand were used as references. Five and four -lines were used for the determination of²³²Th and²²⁶Ra, respectively, to obtain more accurate results. The most significant interferences, caused by the limited energy resolution of the detector, were resolved. In the case of ordinary soils, using one day duration of measurement and 1 kg mass of soil,²³²Th,²²⁶Ra and⁴⁰K can be determined with less than 10% relative random error. Elevated concentrations of²³⁸U(²³⁵U) and²²⁶Ra were observed in soil samples collected around a coal-fired power plant in Ajka town, Hungary.     

Non-destructive compositional analysis of sol–gel synthesized lithium titanate (Li2TiO3) by particle induced gamma-ray emission and instrumental neutron activation analysis

Lithium titanate, one of the important tritium breeding materials in D–T based fusion reactor under ITER programme, was synthesized through sol–gel route. For chemical quality control of finished product, it was necessary to quantify the lithium and titanium contents. As this ceramic sample is difficult to dissolve, non-destructive analytical methods are preferred for compositional analysis. In the present work, two non-destructive nuclear analytical methods namely particle induced gamma-ray emission (PIGE) using proton beam and instrumental neutron activation analysis (INAA) using reactor neutrons were standardized for the determination of lithium and titanium concentrations, respectively and applied to eleven samples of lithium titanate. To the best of our knowledge, Li quantification in lithium titanate sample is being reported for the first time using PIGE. For quantifications of Li and Ti, 478 keV prompt gamma-ray from ⁷Li (p, p′γ) ⁷Li and 320 keV gamma-ray from ⁵⁰Ti (n,γ) ⁵¹Ti were measured, respectively, by high resolution gamma-ray spectrometry. The PIGE and INAA methods were validated using several synthetic samples containing lithium and titanium, respectively. Concentrations of lithium and titanium and Li/Ti mole ratios were evaluated and compared with the stoichiometric concentration of Li₂TiO₃.     

Formation cross section of iron-60 with reactor neutrons in59Fe(n, γ)60Fe reaction

Ingrowth of⁶⁰Co radioactivity in an iron sample irradiated in a nuclear reactor has been measured for determination of formation cross section of⁶⁰Fe in the⁵⁹Fe(n, )⁶⁰Fe reaction with reactor neutrons. After 5 years cooling, the irradiated iron was purified from⁶⁰Co and other radioactive nuclides by an anion exchange separation method and isopropyl ether extraction in hydrochloric acid. The amount of⁶⁰Co ingrowth was measured by -spectrometry using a Ge-detector coupled to a multichannel pulse height analyzer 4 years after the purification of iron. Neutron flux of the irradiation position was calculated from the amount of⁵⁵Fe produced. The observed value of 12.5±2.8 barn is slightly greater than reported value for burnup cross section of⁵⁹Fe(n, x)X, where x refers , , d, p and 2n, and X is any nuclide produced by the above reactions.     

Precise assay of weight per cent sodium in high-level processed nuclear tank waste using a <Superscript>252</Superscript>Cf neutron source

An infrared furnace (ULVAC RHL-410P) was newly applied to the extraction of tritium from concrete samples. After studying the tritium recovery yield regarding temperature and time, the best extraction conditions were set to 800 °C (setting temperature) for 30 minutes under Ar-gas flow of 200 ml/min. Tritium was collected in two cold traps and transferred to a vial for liquid scintillation counting. It took about one hour for the extraction of tritium. Reproducibility and recovery yield of tritium were about 100% compared to the values obtained by the ordinary heating method using an electric furnace. Gamma-ray emitters and tritium of concrete samples collected from several accelerator facilities have been determined. The specific activity of tritium strongly correlated with that of ¹⁵²Eu and ⁶⁰Co, so it was found that tritium was produced by thermal neutron reaction by the ⁶Li(n,)³H reaction. The results indicate that the tritium specific activity in concrete can be estimated from the ⁶⁰Co specific activity obtained easily by -ray measurement.On leave from IHEP, Beijing.This work was supported by Japan Society for the Promotion of Science. The authors also are grateful to Dr. S. Watanabe, Center for Nuclear Study, University of Tokyo, Dr. T. Ohtsuki, Laboratory of Nuclear Science, Tohoku University, and Dr. T. Saito, Research Center for Nuclear Physics, Osaka University, and their colleagues for concrete sampling.     

Elemental Composition Validation from Stored Waveform Inverse Fourier Transform (SWIFT) Isolation FT-ICR MS Isotopic Fine Structure

Elemental composition assignment confidence in mass spectrometry is typically assessed by monoisotopic mass accuracy. For a given mass accuracy, resolution and detection of other isotopologues can further narrow the number of possible elemental compositions. However, such measurements require ultrahigh resolving power and high dynamic range, particularly for compounds containing low numbers of nitrogen and oxygen (both ¹⁵N and ¹⁸O occur at less than 0.4 % natural abundance). Here, we demonstrate validation of molecular formula assignment from isotopic fine structure, based on ultrahigh resolution broadband Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Dynamic range is enhanced by external quadrupole and internal stored waveform inverse Fourier transform (SWIFT) isolation to facilitate detection of low abundance heavy atom isotopologues.